The present invention relates to devices for delivering, injecting, dispensing, infusing and administering substances, and to methods of making and using such devices. More particularly, it relates to a devices for injecting or administering a medicinal fluid product. In some embodiments, the device may be an injection apparatus, such as an injection pen, for self-administering the product.
Injection apparatus or devices are well-known from diabetes therapy, administering growth hormones or osteoporosis preparations. Such devices should on one hand guarantee that the correct dosage is administered and, on the other hand, should be simple and convenient to operate.
An injection apparatus known from WO 97/10865 comprises two casing parts which are screwed together. A reservoir containing a product to be administered is accommodated in one of the casing parts, and a conveying and dosing means is accommodated in the other casing part. The conveying and dosing means includes a piston which is accommodated in the reservoir, and a piston rod which acts on the piston in an advancing direction for delivering a settable dosage. The conveying and dosing means also includes a drive member which can be operated by a user for setting the dosage and delivering it. The drive member is coupled to the piston rod via two spindle drives. The piston rod is linearly guided by the casing part which accommodates the reservoir. Once the reservoir is empty, the user has to rotate the piston rod back while simultaneously pressing on the drive member to reuse the apparatus with a filled reservoir.
An injection apparatus comprising a mechanism which is comparable to the coupling between the piston rod and the drive member is known from WO 99/38554.